Currently, during the process of transmitting speech or audio signals on a network, because the network conditions may vary, the network may intercept the bit stream of the speech or audio signals transmitted from an encoder to the network with different bit rates, so that the decoder may decode the speech or audio signals with different bandwidths from the intercepted bit stream.
In the prior art, because the speech or audio signals transmitted on the network have different bandwidths, the bidirectional switching from/to a narrow frequency band speech or audio signal to/from a wide frequency band speech or audio signal may occur during the process of transmitting speech or audio signals. In embodiments of the present invention, the narrow frequency band signal is switched to a wide frequency band signal with only a low frequency band component through up-sampling and low-pass filtering; the wide frequency band speech or audio signal includes both a low frequency band signal component and a high frequency band signal component.
During the implementation of the present invention, the inventor discovers at least the following problems in the prior art: Because high frequency band signal information is available in wide frequency band speech or audio signals but is absent in narrow frequency band speech or audio signals, when speech or audio signals with different bandwidths are switched, a energy jump may occur in the speech or audio signals resulting in uncomfortable feeling in listening, and thus reducing the quality of audio signals received by a user.